EP2447254A1

EP2447254A1 - Crystals

Info

Publication number: EP2447254A1
Application number: EP10792183A
Authority: EP
Inventors: Hideyuki Itou; Koji Nakamichi; Takashi Tosaka
Original assignee: Nippon Shinyaku Co Ltd
Current assignee: Nippon Shinyaku Co Ltd
Priority date: 2009-06-26
Filing date: 2010-06-25
Publication date: 2012-05-02
Anticipated expiration: 2030-06-25
Also published as: ZA201109099B; RU2556206C3; EP2447254A4; CA2764475A1; NO2447254T3; BRPI1015936B1; CN102459198A; ES2660007T3; HUS1800015I1; US20140155414A1; MA33637B1; WO2010150865A1; LT3275871T; IL216928A0; CA2764475C; EP3275871B1; US9284280B2; KR20120109457A; CY2018011I1; RU2556206C2

Abstract

[Problem] A main object of the present invention is to provide a novel crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide (hereinafter referred to as "compound A").

[Means for Resolution]

A Form-I crystal of compound A, showing diffraction peaks at 9.4 degrees, 9.8 degrees, 17.2 degrees and 19.4 degrees in the powder X-ray diffraction spectrum thereof.

A Form-II crystal of compound A, showing diffraction peaks at 9.0 degrees, 12.9 degrees, 20.7 degrees and 22.6 degrees in the powder X-ray diffraction spectrum thereof.

A Form-III crystal of compound A, showing diffraction peaks at 9.3 degrees, 9.7 degrees, 16.8 degrees, 20.6 degrees and 23.5 degrees in the powder X-ray diffraction spectrum thereof.

Description

[Technical Field]

The present invention relates to a crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide (hereinafter referred to as "compound A").

[Background Art]

Compound A has an excellent PGI2 agonistic effect and shows a platelet aggregation inhibitory effect, a vasodilative effect, a bronchodilative effect, a lipid deposition inhibitory effect, a leukocyte activation inhibitory effect, etc. (see, for example, in Patent Reference 1).
Specifically, compound A is useful as preventive or therapeutic agents for transient ischemic attack (TIA), diabetic neuropathy, diabetic gangrene, peripheral circulatory disturbance (e.g., chronic arterial occlusion, intermittent claudication, peripheral embolism, vibration syndrome, Raynaud's disease), connective tissue disease (e.g., systemic lupus erythematosus, scleroderma, mixed connective tissue disease, vasculitic syndrome), reocclusion/restenosis after percutaneous transluminal coronary angioplasty (PTCA), arteriosclerosis, thrombosis (e.g., acute-phase cerebral thrombosis, pulmonary embolism), hypertension, pulmonary hypertension, ischemic disorder (e.g., cerebral infarction, myocardial infarction), angina (e.g., stable angina, unstable angina), glomerulonephritis, diabetic nephropathy, chronic renal failure, allergy, bronchial asthma, ulcer, pressure ulcer (bedsore), restenosis after coronary intervention such as atherectomy and stent implantation, thrombocytopenia by dialysis, the diseases in which fibrosis of organs or tissues is involved [e.g., Renal diseases (e.g., tuburointerstitial nephritis), respiratory diseases (e.g., interstitial pneumonia (pulmonary fibrosis), chronic obstructive pulmonary disease), digestive diseases (e.g,. hepatocirrhosis, viral hepatitis, chronic pancreatitis and scirrhous stomachic cancer), cardiovascular diseases (e.g, myocardial fibrosis), bone and articular diseases (e.g, bone marrow fibrosis and rheumatoid arthritis), skin diseases (e.g, cicatrix after operation, scalded cicatrix, keloid, and hypertrophic cicatrix), obstetric diseases (e.g., hysteromyoma), urinary diseases (e.g., prostatic hypertrophy), other diseases (e.g., Alzheimer's disease, sclerosing peritonitis, type I diabetes and organ adhesion after operation)], erectile dysfunction (e.g., diabetic erectile dysfunction, psychogenic erectile dysfunction, psychotic erectile dysfunction, erectile dysfunction associated with chronic renal failure, erectile dysfunction after intrapelvic operation for removing prostata, and vascular erectile dysfunction associated with aging and arteriosclerosis), inflammatory bowel disease (e.g., ulcerative colitis, Crohn's disease, intestinal tuberculosis, ischemic colitis and intestinal ulcer associated with Behcet disease), gastritis, gastric ulcer, ischemic ophthalmopathy (e.g., retinal artery occlusion, retinal vein occlusion, ischemic optic neuropathy), sudden hearing loses, avascular necrosis of bone, intestinal damage caused by administration of a non-steroidal anti-inflammatory agent (e.g., diclofenac, meloxicam, oxaprozin, nabumetone, indomethacin, ibuprofen, ketoprofen, naproxen, celecoxib)(there is no particular limitation for the intestinal damage so far as it is damage appearing in duodenum, small intestine and large intestine and examples thereof include mucosal damage such as erosion and ulcer generated in duodenum, small intestine and large intestine), and symptoms associated with lumbar spinal canal stenosis (e.g., paralysis, dullness in sensory perception, pain, numbness, lowering in walking ability, etc. associated with cervical spinal canal stenosis, thoracic spinal canal stenosis, lumbar spinal canal stenosis, diffuse spinal canal stenosis or sacral stenosis) etc. (see, for example, in Patent References 1 to 6). In addition, compound A is useful as an accelerating agent for angiogenic therapy such as gene therapy or autologous bone marrow transplantation, an accelerating agent for angiogenesis in restoration of peripheral artery or angiogenic therapy, etc. (see, for example, in Patent Reference 1).
As mentioned above, while the usefulness of compound A as therapeutic agents for the above-mentioned disorders is known, no reference describes or suggests the possibility of existence of crystals of compound A.

[Prior-Art Reference]

[Patent Reference]

[Patent Reference 1] WO2002/088084
[Patent Reference 2] WO2009/157396
[Patent Reference 3] WO2009/107736
[Patent Reference 4] WO2009/154246
[Patent Reference 5] WO2009/157397
[Patent Reference 6] WO2009/157398

[Summary of the Invention]

[Problem to be Solved by the Invention]

A main object of the present invention is to provide a novel crystal of compound A. Additionally, an object of the present invention is to provide a method for producing the crystal, and a pharmaceutical composition containing the crystal as an active ingredient.

[Means for Solving Problem]

It is hoped that medicament bulk is a thing of a high quality for which constant effect can be always shown and of a form which is handled easily industrially. The present inventors have earnestly studied. As a result, the present inventors have found a novel crystal of compound A, and have completed the present invention.
The present invention includes, for example, the following (1) to (4).

(1) Form-I crystal of compound A which shows diffraction peaks in the powder X-ray diffraction spectrum of compound A (hereinafter referred to as "Form-I crystal of the invention") at the following angles of diffraction 2θ: 9.4 degrees, 9.8 degrees, 17.2 degrees and 19.4 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation (λ = 1.54 Å),
(2) Form-II crystal of compound A which shows diffraction peaks in the powder X-ray diffraction spectrum of compound A (hereinafter referred to as "Form-II crystal of the invention") at the following angles of diffraction 2θ: 9.0 degrees, 12.9 degrees, 20.7 degrees and 22.6 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation (λ = 1.54 Å),
(3) Form-III crystal of compound A which shows diffraction peaks in the powder X-ray diffraction spectrum of compound A (hereinafter referred to as "Form-III crystal of the invention") at the following angles of diffraction 2θ: 9.3 degrees, 9.7 degrees, 16.8 degrees, 20.6 degrees and 23.5 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation (λ = 1.54 Å)
(4) A pharmaceutical composition containing the crystal of one of the above (1) to (3) as the active ingredient (hereinafter referred to as "pharmaceutical composition of the invention").

When specifying an angle of diffraction 2 theta (2θ) for a peak in the invention embodiments and the claims, it should be understood that the value given is to be understood as an interval from said value minus 0.2° to said value plus 0.2°, and preferably from said value minus 0.1° to said value plus 0.1°.

[Brief Description of Drawing]

[Fig. 1] This shows a powder X-ray diffraction spectrum chart of Form-I crystal of the invention. The vertical axis indicates the peak intensity (cps), and the horizontal axis indicates the diffraction angle (2θ[°]).
[Fig. 2] This shows a powder X-ray diffraction spectrum chart of Form-II crystal of the invention. The vertical axis indicates the peak intensity (cps), and the horizontal axis indicates the diffraction angle (2θ[°]).
[Fig. 3] This shows a powder X-ray diffraction spectrum chart of Form-III crystal of the invention. The vertical axis indicates the peak intensity (cps), and the horizontal axis indicates the diffraction angle (2θ[°]).
[Fig. 4] This shows a scanning electron micrograph of Form-I crystal of the invention.
[Fig. 5] This shows a scanning electron micrograph of Form-II crystal of the invention.
[Fig. 6] This shows a scanning electron micrograph of Form-III crystal of the invention.

[Mode for Carrying out the Invention]

Form-I crystal of the invention is characterized in that it shows diffraction peaks at 9.4 degrees, 9.8 degrees, 17.2 degrees and 19.4 degrees in the powder X-ray diffraction spectrum of compound A.
Form-II crystal of the invention is characterized in that it shows diffraction peaks at 9.0 degrees, 12.9 degrees, 20.7 degrees and 22.6 degrees in the powder X-ray diffraction spectrum of compound A.
Form-III crystal of the invention is characterized in that it shows diffraction peaks at 9.3 degrees, 9.7 degrees, 16.8 degrees, 20.6 degrees and 23.5 degrees in the powder X-ray diffraction spectrum of compound A.

A. Production of Compound A

Compound A can be produced, for example, according to the method described in Patent Reference 1, and, it can also be produced according to the production method mentioned below.

Step 1:

6-Iodo-2,3-diphenylpyrazine can be produced from 6-chloro-2,3-diphenylpyrazine by reacting it with sodium iodide. The reaction is carried out in the presence of an acid in an organic solvent (e.g., ethyl acetate, acetonitrile, acetone, methyl ethyl ketone, or their mixed solvent). The acid to be used is, for example, acetic acid, sulfuric acid, or their mixed acid. The amount of sodium iodide to be used is generally within a range of from 1 to 10 molar ratio relative to 6-chloro-2,3-diphenylpyrazine, preferably within a range of from 2 to 3 molar ratio. The reaction temperature varies depending on the kinds of the materials and the acid to be used, but may be generally within a range of from 60°C to 90°C. The reaction time varies depending on the kinds of the materials and the acid to be used and on the reaction temperature, but may be generally within a range of from 9 hours to 15 hours.

Step 2:

5,6-Diphenyl-2-[4-hydroxybutyl(isopropyl)amino]pyrazine can be produced from 6-iodo-2,3-diphenylpyrazine by reacting it with 4-hydroxybutyl(isopropyl)amine. The reaction is carried out in the presence of a base in an organic solvent (e.g., sulfolane, N-methylpyrrolidone, N,N-dimethylimidazolidinone, dimethyl sulfoxide or their mixed solvent). The base to be used is, for example, sodium hydrogencarbonate, potassium hydrogencarbonate, potassium carbonate, sodium carbonate or their mixed base. The amount of 4-hydroxybutyl(isopropyl)amine to be used may be generally within a range of from 1.5 to 5.0 molar ratio relative to 6-iodo-2,3-diphenylpyrazine, preferably within a range of from 2 to 3 molar ratio. The reaction temperature varies depending on the kinds of the materials and the base to be used, but may be generally within a range of from 170°C to 200°C. The reaction time varies depending on the kinds of the materials and the base to be used and on the reaction temperature, but may be generally within a range of from 5 hours to 9 hours.

Step 3:

Compound A can be produced from 5,6-diphenyl-2-[4-hydroxybutyl(isopropyl)amino]pyrazine by reacting it with N-(2-chloroacetyl)methanesulfonamide. The reaction is carried out in the presence of a base in a solvent (N-methylpyrrolidone, 2-methyl-2-propanol or their mixed solvent). The base to be used is, for example, potassium t-butoxide, sodium t-butoxide or their mixed base. The amount of N-(2-chloroacetyl)methanesulfonamide to be used may be generally within a range of from 2 to 4 molar ratio relative to 5,6-diphenyl-2-[4-hydroxybutyl(isopropyl)amino]pyrazine, preferably within a range of from 2 to 3 molar ratio. The reaction temperature varies depending on the kinds of the materials and the base to be used, but may be generally within a range of from -20°C to 20°C. The reaction time varies depending on the kinds of the materials and the base to be used and on the reaction temperature, but may be generally within a range of from 0.5 hours to 2 hours.
The compounds to be used as the starting materials in the above-mentioned production method for compound A are known compounds, or can be produced by known methods.

B. Productions of Form-I Crystal of the Invention, Form-II Crystal of the Invention, and Form-III Crystal of the Invention (hereinafter collectively referred to as "the crystals of the invention")

(I) Production of Form-I Crystal of the Invention

Form-I crystal of the invention can be produced, for example, according to the method described below.

(1) Dissolution step

This step is a step of dissolving compound A in a solvent by heating. The suitable solvent to be used in the step is, for example, alcoholic solvent, a mixed solvent of alcoholic solvent and ketone solvent. The suitable alcoholic solvent to be used in the step is, for example, methanol, ethanol, 2-propanol, preferably ethanol. The suitable ketone solvent to be used in the step is, for example, methylethylketone.
Especially, the preferable solvent to be used in the step is ethanol or a mixed solvent of ethanol and methylethylketone. In case of a mixed solvent of ethanol and methylethylketone, ethanol is within a range of from 1.5-fold (v/v) to 100-fold (v/v) relative to the amount of methylethylketone, preferably within a range of from 3-fold (v/v) to 50-fold (v/v), more preferably within a range of from 6-fold (v/v) to 20-fold (v/v).
The total volume of the solvent to be used in the step is preferably within a range of from 2-fold (mL/g) to 30-fold (mL/g) relative to the amount of compound A, more preferably within a range of from 3-fold (mL/g) to 20-fold (mL/g), further more preferably within a range of from 4-fold (mL/g) to 15-fold (mL/g). The heating temperature varies depending on the kind of solvent and the volume of the solvent used, but generally is lower than the boiling point of the solvent to be used, and is preferably within a range of from 60°C to 100°C, more preferably within a range of from 70°C to 90°C.
In the step, the solution may be filtered to remove insolubles, if necessary. To prevent the precipitation of crystals during the filtration, the filtration is preferably carried out under pressure using a funnel equipped with a heating device. In case the precipitation of crystals is observed in the filtrate, the precipitate is preferably dissolved again by reheating after the filtration.

(2) Cooling step

This step is a step of precipitating Form-I crystal of the invention from the solution prepared in the above step (1) by cooling. The step is preferably carried out by using a crystallizer equipped with a heating function and a stirring function.
The cooling temperature (temperature when precipitated crystal is collected) is, suitably, within a range of from -10°C to 50°C, preferably within a range of from 0°C to 20°C, and more preferably within a range of from 0°C to 10°C. The step is preferably carried out by cooling within a range of from 3 hours to 95 hours slowly until reaching the cooling temperature.
Additionally, in the step, a seed of Form-I crystal of the invention may be added. In that case, it is preferable that the seed of Form-I crystal of the invention is added when the solution is cooled to a temperature within a range of from 60°C to 90°C. The amount of the seed crystal of Form-I crystal of the invention is preferably within a range of from 1% to 10% by weight relative to the amount of compound A.

(3) Crystal collection and drying step

This step is a step of collecting the precipitated crystal obtained in the above step (2) using a known means such as filtration and centrifugation, and drying the collected crystal.
A drying step can be carried out by a conventional method such as drying under reduced pressure and over a desiccant. Drying is preferably carried out under reduced pressure (e.g., 10 mmHg or less) at within a range of from 20°C to 70°C for one hour to 48 hours.
Additionally, following the above step (1), after partially precipitating crystal by removing the solvent while heating and stirring the solution prepared in the above step (1), Form-I crystal of the invention can be obtained by carrying out the above steps (2) and (3). In the step of removing the solvent, the seed of Form-I crystal of the invention may be added. The amount of the seed of Form-I crystal of the invention is preferably within a range of from 0.1% to 10% by weight relative to the amount of compound A used in the above step (1).

(II) Production of Form-II Crystal of the Invention

Form-II crystal of the invention can be produced, for example, according to the method described below.

(1) Dissolution Step

This step is a step of dissolving compound A in a solvent by heating. The suitable solvent to be used in the step is, for example, alcoholic solvent, ketone solvent, a saturated hydrocarbon solvent, ether solvent, and water, or a mixed solvent thereof. The preferable mixed solvent is a mixture of ether solvent and a saturated hydrocarbon solvent or water, or a mixture of alcohol solvent and ketone solvent or water.
The alcoholic solvent to be used in the step is, for example, a straight or branched alcohol having one to 8 carbon atoms. Specifically, the alcohol solvent may include methanol, ethanol, n-propanol, isopropanol, 1-butanol, 2-butanol, t-butanol, 1-amylalcohol, 1-hexanol, 1-heptanol, I-octanol. The ether solvent to be used in the step may include tetrahydrofuran, 1,4-dioxane. The saturated hydrocarbon solvent to be used in the step is, for example, a straight or branched alkane having 6 to 8 carbon atoms, or a cycloalkane having having 6 to 8 carbon atoms. Specifically, the saturated hydrocarbon solvent may include heptane, octane, cyclohexane, cycloheptane, cyclooctane. The ketone solvent to be used in the step is, for example, a straight or branched one having 3 to 8 carbon atoms. Specifically, the ketone solvent may include acetone, methylethylketone.
The total volume of the solvent to be used in the step is suitably within a range of from 2-fold (mL/g) to 20-fold (mL/g) relative to the amount of compound A, preferably within a range of from 3-fold (mL/g) to 15-fold (mL/g), more preferably within a range of from 5-fold (mL/g) to 10-fold (mL/g). The heating temperature varies depending on the kind of solvent and the volume of the solvent used, but generally is lower than the boiling point of the solvent to be used, and is preferably within a range of from 60°C to 90°C, more preferably within a range of from 70°C to 80°C.
In the step, the solution may be filtered to remove insolubles, if necessary. To prevent the precipitation of crystals during the filtration, the filtration is preferably carried out under pressure using a funnel equipped with a heating device. In case the precipitation of crystals is observed in the filtrate, the precipitate is preferably dissolved again by reheating after the filtration.

(2) Cooling step

This step is a step of precipitating Form-II crystal of the invention from the solution prepared in the above step (1) by cooling. The step is preferably carried out by using a crystallizer equipped with a heating function and a stirring function.
The cooling temperature (temperature when precipitated crystal is collected) is suitably within a range of from -10°C to 50°C, preferably within a range of from 0°C to 20°C, and more preferably within a range of from 0°C to 10°C.
Additionally, in the step, a seed of Form-II crystal of the invention may be added. The amount of the seed of Form-II crystal of the invention is preferably within a range of from 1% to 10% by weight relative to the amount of compound A.
In case Form-II crystal of the invention is produced by using alcoholic solvent or a mixture of alcoholic solvent and ketone solvent as a solvent, it is necessary that the seed of Form-II crystal of the invention be added in the solution prepared in the above step (1) and the solution be cooled, or the solution prepared in the above step (1) be cooled rapidly. The cooling rate is suitably within a range of from 60°C/hour to 600°C/hour.

(3) Crystal collection and drying step

This step is the same as the method described above in "(3) Crystal collection and drying step" in the above-mentioned "(I) Production of Form-I Crystal of the Invention."

(III) Production of Form-III Crystal of the Invention

Form-III crystal of the invention can be produced, for example, according to the method described below.

(1) Dissolution step

This step is a step of dissolving compound A in a solvent by heating. The suitable solvent to be used in the step is, for example, ester solvent, aromatic hydrocarbon solvent. The suitable ester solvent to be used in the step is, for example, diethylcarbonate, n-butyl acetate, isoamyl acetate, n-amyl acetate, preferably n-butyl acetate. The suitable aromatic hydrocarbon solvent to be used in the step is, for example, ethylbenzene.
The total volume of the solvent to be used in the step is suitably within a range of from 5-fold (mL/g) to 30-fold (mL/g) relative to the amount of compound A, preferably within a range of from 7-fold (mL/g) to 20-fold (mL/g), more preferably within a range of from 10-fold (mL/g) to 15-fold (mL/g). The heating temperature varies depending on the kind of solvent and the volume of the solvent used, but generally is lower than the boiling point of the solvent to be used, preferably within a range of from 40°C to 90°C, and more preferably within a range of from 50°C to 80°C.
In the step, the solution may be filtered to remove insolubles, if necessary. To prevent the precipitation of crystals during the filtration, the filtration is preferably carried out under pressure using a funnel equipped with a heating device. In case the precipitation of crystals is observed in the filtrate, the precipitate is preferably dissolved again by reheating after the filtration.

(2) Cooling step

This step is a step of precipitating Form-III crystal of the invention from the solution prepared in the above step (1) by cooling. The step is preferably carried out using a crystallizer equipped with a heating function and a stirring function.
The cooling rate is suitably within a range of from 0.5°C/hour to 120°C/hour. The cooling temperature (temperature when precipitated crystal is collected) is suitably within a range of from -10°C to 30°C, preferably within a range of from 0°C to 20°C, and more preferably within a range of from 0°C to 10°C.

(3) Crystal collection and drying step

The step is the same as the method described above in "(3) Crystal collection and drying step" in the above-mentioned "(I) Production of Form-I Crystal of the Invention."

C. Medical Use and Pharmaceutical Composition of the Invention

Compound A according to the present invention has an excellent PGI2 agonistic effect and shows a platelet aggregation inhibitory effect, a vasodilative effect, a bronchodilative effect, a lipid deposition inhibitory effect, a leukocyte activation inhibitory effect, etc.
Therefore, the crystals of the invention or the pharmaceutical composition of the invention is useful as preventive or therapeutic agents for transient ischemic attack (TIA), diabetic neuropathy, diabetic gangrene, peripheral circulatory disturbance (e.g., chronic arterial occlusion, intermittent claudication, peripheral embolism, vibration syndrome, Raynaud's disease), connective tissue disease (e.g., systemic lupus erythematosus, scleroderma, mixed connective tissue disease, vasculitic syndrome), reocclusion/restenosis after percutaneous transluminal coronary angioplasty (PTCA), arteriosclerosis, thrombosis (e.g., acute-phase cerebral thrombosis, pulmonary embolism), hypertension, pulmonary hypertension, ischemic disorder (e.g., cerebral infarction, myocardial infarction), angina (e.g., stable angina, unstable angina), glomerulonephritis, diabetic nephropathy, chronic renal failure, allergy, bronchial asthma, ulcer, pressure ulcer (bedsore), restenosis after coronary intervention such as atherectomy and stent implantation, thrombocytopenia by dialysis, the diseases in which fibrosis of organs or tissues is involved [e.g., renal diseases (e.g., tuburointerstitial nephritis), respiratory diseases (e.g., interstitial pneumonia (pulmonary fibrosis), chronic obstructive pulmonary disease), digestive diseases (e.g,. hepatocirrhosis, viral hepatitis, chronic pancreatitis and scirrhous stomachic cancer), cardiovascular diseases (e.g, myocardial fibrosis), bone and articular diseases (e.g, bone marrow fibrosis and rheumatoid arthritis), skin diseases (e.g, cicatrix after operation, scalded cicatrix, keloid, and hypertrophic cicatrix), obstetric diseases (e.g., hysteromyoma), urinary diseases (e.g., prostatic hypertrophy), other diseases (e.g., Alzheimer's disease, sclerosing peritonitis, type I diabetes and organ adhesion after operation)], erectile dysfunction (e.g., diabetic erectile dysfunction, psychogenic erectile dysfunction, psychotic erectile dysfunction, erectile dysfunction associated with chronic renal failure, erectile dysfunction after intrapelvic operation for removing prostata, and vascular erectile dysfunction associated with aging and arteriosclerosis), inflammatory bowel disease (e.g., ulcerative colitis, Crohn's disease, intestinal tuberculosis, ischemic colitis and intestinal ulcer associated with Behcet disease), gastritis, gastric ulcer, ischemic ophthalmopathy (e.g., retinal artery occlusion, retinal vein occlusion, ischemic optic neuropathy), sudden hearing loss, avascular necrosis of bone, intestinal damage caused by administration of a non-steroidal anti-inflammatory agent (e.g., diclofenac, meloxicam, oxaprozin, nabumetone, indomethacin, ibuprofen, ketoprofen, naproxen, celecoxib)(there is no particular limitation for the intestinal damage so far as it is damage appearing in duodenum, small intestine and large intestine and examples thereof include mucosal damage such as erosion and ulcer generated in duodenum, small intestine and large intestine), and symptoms associated with lumbar spinal canal stenosis (e.g., paralysis, dullness in sensory perception, pain, numbness, lowering in walking ability, etc. associated with cervical spinal canal stenosis, thoracic spinal canal stenosis, lumbar spinal canal stenosis, diffuse spinal canal stenosis or sacral stenosis) etc. In addition, the crystals of the invention or the pharmaceutical composition of the invention is also useful as an accelerating agent for angiogenic therapy in gene therapy or autologous bone marrow transplantation, an accelerating agent for angiogenesis in restoration of peripheral artery or angiogenic therapy, etc. If the crystals of the invention are administered as a medicine, the pharmaceutical composition of the invention is the crystals of the invention as it is or contains the crystals of the invention in a pharmaceutically acceptable, nontoxic and inert carrier within a range of from 0.1% to 99.5%, preferably within a range of from 0.5% to 90%.
Examples of the carrier include solid, semi-solid or liquid diluent, filler and other auxiliary agents for pharmaceutical formulation. These can be used alone or as a mixture of two or more thereof.
The pharmaceutical composition of the invention may be in any of the forms of oral preparations such as powder, capsules, tablets, sugar-coated tablets, granules, diluted powder, suspension, liquid, syrup, elixir or troche, and parenteral preparations such as injection or suppository in a solid or liquid dose unit. It may also be in a form of a sustained release preparation. Among them, oral preparations such as tablets are particularly preferred. Powder is able to be manufactured by making the crystals of the invention into an appropriate fine size. Diluted powder is able to be manufactured by such a manner that the crystals of the invention are made into an appropriate fine size and then mixed with a pharmaceutical carrier which is similarly made into a fine size such as edible carbohydrate (e.g., starch and mannitol). Flavoring agent, preservative, dispersing agent, coloring agent, perfume, etc. may be optionally added thereto.
Capsules are able to be manufactured by such a manner that the powder or diluted powder which is made powdery as mentioned above or granules which will be mentioned under the item for tablets are filled in an capsule shell such as gelatin capsule. It is also possible to manufacture in such a manner that the powder or the diluted powder in a powdery form is mixed with a lubricant or a fluidizing agent such as colloidal silica, talc, magnesium stearate, calcium stearate or solid polyethylene glycol followed by subjecting it to a filling operation. When a disintegrating agent or solubilizing agent such as carboxymethyl cellulose, carboxymethyl cellulose calcium, lowly-substituted hydroxypropyl cellulose, croscarmellose sodium, carboxymethyl starch sodium, calcium carbonate or sodium carbonate is added, efficacy of the pharmaceutical when the capsules are ingested can be improved. It is also possible that fine powder of the crystals of the invention is suspended/dispersed in vegetable oil, polyethylene glycol, glycerol or surfactant and wrapped with a gelatin sheet to give a soft capsule preparation.
Tablets are able to be manufactured in such a manner that a powdery mixture is prepared by addition of a filler to the crystals of the invention which have been made powdery and made into granules or slugs and then a disintegrating agent or a lubricant is added thereto followed by making them into tablets.
The powdery mixture is able to be manufactured by mixing appropriately powdered crystals of the invention with a diluent or a base. If necessary, it is possible to add a binder (such as carboxymethyl cellulose sodium, methyl cellulose, hydroxypropyl methyl cellulose, gelatin, polyvinylpyrrolidone or polyvinyl alcohol), a dissolution retarding agent (such as paraffin), a reabsorbing agent (such as a quaternary salt), an adsorbent (such as bentonite or kaolin), etc. thereto.
The powdery mixture is able to be made into granules in such a manner that it is firstly made wet by using a binder, for example, syrup, starch paste, acacia, cellulose solution or polymer solution, mixed with stirring and dried followed by grinding. Instead of making the powder into granules as such, it is also possible that the powder is applied to a tabletting machine and the resulting slug in an incomplete shape is ground to give granules. When a lubricant such as stearic acid, stearate, talc or mineral oil is added to the granules prepared as such, sticking of the granules to each other can be prevented.
Tablets are also able to be manufactured in such a manner that the crystals of the invention are mixed with a fluid inert carrier and then directly making them into tablets without conducting the above steps of making them into granules or slugs.
The tablets prepared as such can be subjected to film coating or sugar coating. It is also possible to apply a transparent or semi-transparent protective coat made of a tightly closed shellac film, a coat made of sugar or polymer material, or a polished coat made of wax.
In other oral preparations such as liquid, syrup, troche or elixir, it is also possible to make it into a dose unit form wherein a predetermined amount thereof contains a predetermined amount of the crystal of the present invention.
The syrup is able to be manufactured by dissolving the crystals of the invention into an appropriate aqueous solution of a flavor. The elixir is able to be manufactured by using a non-toxic alcoholic carrier.
The suspension is able to be manufactured by dispersing the crystals of the invention into a non-toxic carrier. If necessary, it is possible to add a solubilizing agent or an emulsifier (such as ethoxylated isostearyl alcohol and polyoxyethylene sorbitol ester), a preservative or a flavor-endowing agent (such as peppermint oil or saccharine) thereto.
If necessary, the dose unit formulation for oral administration may be made into microcapsules. The formulation is also able to be coated or embedded into polymer or wax to obtain a prolonged action or sustained release of the active ingredient.
The parenteral preparation may be in a liquid dose unit form for subcutaneous, intramuscular or intravenous injection such as in a form of solution or suspension. The parenteral preparation is able to be manufactured in such a manner that a predetermined amount of the crystals of the invention is suspended or dissolved in a non-toxic liquid carrier meeting the purpose of injection such as aqueous or oily medium and then the suspension or solution is sterilized. Non-toxic salt or a solution thereof may be added thereto for making the injection solution isotonic. It is also possible to add a stabilizer, a preservative, an emulsifier and the like.
The suppository is able to be manufactured by dissolving or suspending the crystals of the invention in a low-melting and water-soluble or insoluble solid such as polyethylene glycol, cacao fat, semi-synthetic fat/oil (such as Witepsol (registered trade mark)), higher ester (such as myristyl palmitate ester) or a mixture thereof.
Although the dose may vary depending upon the state of a patient such as body weight or age, administering route or degree of symptom, a range of from 0.001 mg to 100 mg per day as an amount of the crystals of the invention is generally suitable for an adult and a range of from 0.01 mg to 10 mg is more preferable. In some cases, a dose less than the above may be sufficient or, on the other hand, a dose more than the above may be necessary. It is also possible to administer one to several times a day or to administer with an interval of one to several days.

[Examples]

The present invention is described in more detail with reference to Examples and Test Examples given below; however, the present invention should not be limited whatsoever to these Examples.
For the powder X-ray diffractometry, Rigaku Corporation's RINT-Ultima III (target: Cu, voltage: 40 kV, current: 40 mA, scan speed: 4 degrees/min) was used.

Example 1: Production of Form-I Crystal of the Invention

Ethanol (440 ml) was added to compound A (40 g), and the mixture was stirred and heated in an oil bath of 100°C to 110°C. After compound A was dissolved, ethanol (280 ml) was removed. The obtained concentrate was stirred and heated under reflux in a water bath of 80°C for 1 hour. The solution was gradually cooled to 10°C in 20 hours while stirring, and the precipitated crystal was collected through filtration. The obtained crystal was washed with a small amount of ethanol (48 ml), and dried under reduced pressure at 60°C to give Form-I crystal of the invention (38.93 g, 97.3 %). A powder X-ray diffraction spectrum of the Form-I crystal of the invention is shown in Fig. 1.
Mp: 140.4°C (the Japanese Pharmacopoeia, method 1 of Melting Point Determination)

Example 2: Production of Form-I Crystal of the Invention

Ethanol (99 g) and methylethylketone (11g) were added to compound A (20 g), and heated at 77°C to dissolve compound A, and then the solution was gradually cooled to 10°C in 20 hours. During cooling, to the solution was added a small amount of Form-I crystal of the invention. After cooling, the precipitated crystal was collected through filtration, washed with ethanol, and dried under reduced pressure to give Form-I crystal of the invention (18.72 g, 93.6 %).

Example 3: Production of Form-II Crystal of the Invention

Ethanol (550 g) and methyl ethyl ketone (55 g) were added to compound A (100 g), heated at 77°C, and filtered under pressure while kept heated. With stirring, the resulting filtrate was cooled from 70°C to 0°C, taking 30 minutes, and after reaching 0°C, this was stirred at 0°C for 2.5 hours. The precipitated crystal was collected through filtration, washed with ethanol (200 ml), and dried under reduced pressure. Ethanol (99 g) and methyl ethyl ketone (11 g) were added to the obtained crystal (20 g), heated at 70°C, then kept at 70°C for 1 hour, and gradually cooled to 10°C, taking 20 hours; and after reaching 10°C, this was stirred at 10°C for 1 hour. The precipitated crystal was collected through filtration, washed with ethanol (40 ml), and dried under reduced pressure to give Form-II crystal of the invention (18.73 g, 93.7 %). A powder X-ray diffraction spectrum of Form-II crystal of the invention is shown in Fig. 2.
Mp: 135.2°C (the Japanese Pharmacopoeia, method 1 of Melting Point Determination)

Example 4: Production of Form-II Crystal of the Invention

Ethanol (99 g) and methylethylketone (11g) were added to compound A (20 g), and heated at 77°C to dissolve compound A, and then the solution was gradually cooled to 10°C in 20 hours. During cooling, to the solution was added a small amount of Form-II crystal of the invention. After cooling, the precipitated crystal was collected through filtration, washed with ethanol, and dried under reduced pressure to give Form-II crystal of the invention (19.70 g, 98.5 %).

Example 5: Production of Form-III Crystal of the Invention

N-Butyl acetate (500 ml) was added to compound A (36.7 g), and heated at 75°C to dissolve compound A, and then cooled to 5°C. Then, a process of heating to 60°C and cooling to 5°C was carried out, and the process was repeated. The precipitated crystal was collected through filtration, washed with a small amount of isopropyl acetate (50 ml), and dried under reduced pressure to give Form-III crystal of the invention (29.0 g, 79.0 %). A powder X-ray diffraction spectrum of Form-III crystal of the invention is shown in Fig. 3.
Mp: 138.0°C (the Japanese Pharmacopoeia, method 1 of Melting Point Determination)
The crystals of the invention used in the following Test Examples 1 to 3 were prepared by the following method.
Form-I crystal of the invention, Form-II crystal of the invention, and Form-III crystal of the invention were prepared in the same methods as in Example 2, Example 4, and Example 5, respectively.

Test Example 1: Measurement of Particle Size

(1) Measurement of Particle Size Distribution of the Crystals of the Invention

After a dispersant (10 mL) was added to the crystals of the invention (20 mg) followed by shaking up, the crystals of the invention were dispersed with ultrasonic wave. The particle size distributions of the crystals of the invention were measured by using HORIBA LA-910. The result is shown in Table 1.
The dispersant used is a filtered saturated solution of compound A in 0.1 v/v% Polysorbate 80 aqueous solution.

[Table 1]

	Crystal Form	D10	D50	D90
1	Form-I Crystal of the Invention	5.6	12.8	25.8
2	Form-II Crystal of the Invention	5.2	11.3	22.0
3	Form-III Crystal of the Invention	4.3	8.0	14.4

D10 : Cumulative undersize particle diameter at 10% of volumetric ratio [µm]
D50 : Cumulative undersize particle diameter at 50% of volumetric ratio [µm]
D90 : Cumulative undersize particle diameter at 90% of volumetric ratio [µm]

(2) Observation of the Crystals of the Invention with Electron Scanning Microscope

The crystals were observed through an electron scanning microscope (HITACHI HIGH TECHNOLOGIES TM-1000 Miniscope).
Fig.4 shows the electron scanning micrograph of Form-I crystal of the invention. Fig.5 shows that of Form-II crystal and Fig.6 shows that of Form-III crystal.
From the results of (1) and (2) mentioned above, it was concluded that the particle size of Form-I crystal of the invention is larger than those of Form-II and Form-III crystals.

Test Example 2: Measurement of Residual Solvent Contained in Crystals of the Invention

The concentration of residual solvent contained in the crystals of the invention was measured by using the following measurement conditions. The result is shown in Table 2.

(Measurement Conditions)

GC Apparatus

Detector: Flame Ionization Detector
Column: Capillary Column
Column Temperature: 150°C - 230°C
Injection Temperature: 200°C
Detector Temperature: 300°C
Carrier Gas: Helium

[Table 2]

	Crystal Form	Solvent	Content (ppm)
1	Form-I Crystal of the Invention	Ethanol	371
1	Form-I Crystal of the Invention	Methyl-ethyl-ketone	82
2	Form-II Crystal of the Invention	Ethanol	2169
		Methyl-ethyl-ketone	246
3	Form-III Crystal of the Invention	Isopropyl acetate	93
3	Form-III Crystal of the Invention	n-Butyl acetate	2781

Although each crystal Form did not contain a considerable amount of residual solvents, the amount of the residual solvents in Form-I crystal of the invention was less than those of Form-II and Form-III.

Test Example 3: Impurity-Removing Effect in Recrystallization

The effectiveness of removing impurities in the course of the recrystallization of each crystal form was measured by using the following measurement conditions (reversed-phase liquid chromatography).

(Measurement Conditions)

HPLC Apparatus

Detector: Ultraviolet Absorption Detector
Column: ODS Column
Column Temperature: 40°C
Mobile Phase: Mixture of Water, Acetonitrile and Methanesulfonic acid

The purity (%) of each crystal of compound A was calculated by the following equation. $Purity (%) = (Peak area of compound A) / (Total area) \times 100$
The removal ratio of impurities (%) for each crystal was calculated by the following equation. $Removal ratio of impurities (%) = \{[(Purity of each crystal of compound A) - (Purity of crude compound A)] / [100 - (Purity of crude compound A)]\} \times 100$

The result is shown in Table 3.

[Table 3]

	Crystal Form	Purity of Compound A (%)	Ratio of Impurity Removal (%)
	Crude Material	98.04
1	Form-I Crystal of the Invention	99.51	75
2	Form-II Crystal of the Invention	99.33	66
3	Form-III Crystal of the Invention	98.97	47

From the result shown in Table 3, the effectiveness of removing impurities for Form-I crystal of the invention was the highest compared with those for Form-II and III crystals.

Test Example 4: Investigation of Solvent for Crystallization of Compound A

Investigations of crystallization of compound A were executed according to the methods of the following (1) and (2).

(1) Crystallization solvent (see Tables 4 and 5) was added to compound A, and the mixture was stirred at 50°C for 60 minutes. The resulting mixture was filtered. After the filtration, the isolated mother liquor was stirred at 60°C for 30 minutes, and cooled down to 5°C over 11 hours. After stirring at 5°C for 72 hours, the precipitated solid was collected by filtration. The solid was dried at 20°C under reduced pressure, whereby a solid was obtained.

Powder X-ray diffraction spectrums of the obtained crystals were measured and the form of each crystal was determined.
The results are shown in Table 4 (investigation by single solvents) and Table 5 (investigation by mixed solvents).

In the investigation by mixed solvents (Table 5), each solvent was mixed and used in an equal amount.

[Table 4]

	Crystallization Solvent	Crystal Form
1	tert-Butyl methyl ether	NA
2	Acetone	Form-II Crystal of the Invention + Form-III Crystal of the Invention
3	Chloroform	NA
4	Methanol	Form-II Crystal of the Invention + Form-III Crystal of the Invention
5	Tetrahydrofuran	Form-II Crystal of the Invention + Form-III Crystal of the Invention
6	Isopropyl ether	NA
7	2-Methyltetrahydrofuran	Form-II Crystal of the Invention + Form-III Crystal of the Invention
8	Ethanol	NA
9	Cyclohexane	NA
10	Acetonitrile	Form-II Crystal of the Invention + Form-III Crystal of the Invention
11	1,2-Dichloroethane	NA
12	Fluorobenzene	Form-II Crystal of the Invention + Form-III Crystal of the Invention
13	1,2-Dimethoxyethane	Form-II Crystal of the Invention + Form-III Crystal of the Invention
14	Methylcyclohexane	NA
15	Nitromethane	Form-II Crystal of the Invention + Form-III Crystal of the Invention
16	1,4-Dioxane	NA
17	3,3-Dimethyl-2-butanone	Form-II Crystal of the Invention + Form-III Crystal of the Invention
18	Isobutanol	NA
19	Toluene	Form-II Crystal of the Invention + Form-III Crystal of the Invention
20	Diethylcarbonate	Form-III Crystal of the Invention
21	n-Butyl acetate	Form-III Crystal of the Invention
22	Chlorobenzene	Form-II Crystal of the Invention + Form-III Crystal of the Invention
23	Ethylbenzene	NA
24	p-Xylene	NA
25	Isoamyl acetate	Form-III Crystal of the Invention
26	n -Amyl acetate	Form-III Crystal of the Invention
27	Methyl-phenyl-ether	Form-II Crystal of the invention + Form-III Crystal of the invention
28	Cyclohexanone	NA
29	bis(2-Methoxy ethyl)ether	Form-III Crystal of the invention
30	1,3,5-Trimethylbenzene	Amorphous
31	4-Hydroxy-4-methyl-2-pentanone	Form-II Crystal of the invention + Form-III Crystal of the invention
32	2,6-Dimethyl-4-heptanone	Form-III Crystal of the invention

NA: Solid was not precipitated.

[Table 5]

	Crystallization Solvent	Crystal Form
1	Chloroform	NA
1	Acetonitrile	NA
2	Tetrahydrofuran	Form-II Crystal of the Invention
2	Cyclohexane	Form-II Crystal of the Invention
3	Ethyl formate	Form-II Crystal of the Invention + Form-III Crystal of the invention
3	Water
4	Methanol	NA
4	Water	NA
5	Acetonitrile	Form-17 Crystal of the Invention + Form-III Crystal of the Invention
5	Water
6	1,2-Dimethoxyethane	Form-II Crystal of the Invention + Form-III Crystal of the Invention
6	Water
7	Ethanol	Form-II Crystal of the Invention
7	Water	Form-II Crystal of the Invention
8	Cyclohexane	Form-II Crystal of the Invention
8	1,4-Dioxane	Form-II Crystal of the Invention
9	2-Propanol	Form-II Crystal of the Invention
9	Water	Form-II Crystal of the Invention
10	Cyclohexanone	NA
10	Tetrahydrofuran	NA
11	1-Propanol	Form-II Crystal of the Invention
11	Water	Form-II Crystal of the Invention
12	1,4-Dioxane	Form-II Crystal of the Invention
12	Water	Form-II Crystal of the Invention
13	2-Butanol	Form-II Crystal of the Invention
13	Water	Form-II Crystal of the Invention
14	Cyclohexanone	Form-II Crystal of the Invention + Form-III Crystal of the Invention
14	Cyclohexane
15	1-Butanol	Form-II Crystal of the Invention
15	Water	Form-II Crystal of the Invention
16	Cyclohexanone	Forum-11 Crystal of the Invention + Form-III Crystal of the Invention
16	1,4-Dioxane

NA: Solid was not precipitated.

(2) Further investigations were executed using the following method for those conditions under which crystals were not precipitated (see Tables 4 and 5) and conditions similar to them. The solvents used in the further experiments were selected in consideration of toxicity, solubility of compound A and availability for industrial use.

An amount of solvent less than that of the test in the above-mentioned (1) was added to compound A, and the mixture was heated to 75°C with stirring. After dissolving compound A, the mixture was stirred at 65°C for 5 to 8 hours. The mixture was cooled down to 20°C over 9 hours. The precipitated crystal was collected by filtration and dried at 70°C under reduced pressure, whereby a crystal was obtained. The results are shown in Table 6.

In the investigation by mixed solvents, each solvent was mixed and used in an equal amount.

[Table 6]

	Crystallization Solvent	Crystal Form
1	tert-Butyl methyl ether	NA
2	Isopropyl ether	NA
3	Cyclohexane	NA
4	Ethanol	Form-I Crystal of the Invention
5	2-Propancl	Form-I Crystal of the Invention + Form-III Crystal of the Invention
6	Ethylbenzene	Form-III Crystal of the Invention
7	Methanol	Form-I Crystal of the Invention + Form-III Crystal of the Invention
7	Water
8	Cyclohexanone	NA
8	Tetrahydrofuran	NA

NA: Solid was not precipitated.

From the results of the above-mentioned (1) and (2), it was concluded that Form-II crystal of the invention and Form-III crystal of the invention can be obtained from various solvents.
On the other hand, crystals which contain Form-I crystal of the invention could be obtained only from alcohol solvents, and highly pure Form-I crystal of the invention could be obtained from ethanol.

Claims

A Form-I crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide, showing diffraction peaks in its X-ray powder diffraction spectrum at least at the following angles of diffraction 2θ: 9.4 degrees, 9.8 degrees, 17.2 degrees and 19.4 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation.
A Form-II crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide, showing diffraction peaks in its X-ray powder diffraction spectrum at least at the following angles of diffraction 2θ: 9.0 degrees, 12.9 degrees, 20.7 degrees and 22.6 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation.
A Form-III crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide, showing diffraction peaks in its X-ray powder diffraction spectrum at least at the following angles of diffraction 2θ: 9.3 degrees, 9.7 degrees, 16.8 degrees 20.6 degrees and 23.5 degrees, wherein the X-ray powder diffraction diagram is obtained by using Cu Kα radiation.
A pharmaceutical composition comprising the crystal of any one of claims 1 to 3 as an active ingredient.
A PGI2 receptor agonist agent comprising the crystal of any one of claims 1 to 3 as an active ingredient.
A preventive or therapeutic agent for transient ischemic attack, diabetic neuropathy, diabetic gangrene, peripheral circulatory disturbance, connective tissue disease, reocclusion / restenosis after percutaneous transluminal coronary angioplasty (PTCA), arteriosclerosis, thrombosis, hypertension, pulmonary hypertension, ischemic disorder, angina, glomerulonephritis, diabetic nephropathy, chronic renal failure, allergy, bronchial asthma, ulcer, pressure ulcer (bedsore), restenosis after coronary intervention such as atherectomy and stent implantation, thrombocytopenia by dialysis, the diseases in which fibrosis of organs or tissues is involved, erectile dysfunction, inflammatory bowel disease, gastritis, gastric ulcer, ischemic ophthalmopathy, sudden hearing loss, avascular necrosis of bone, intestinal damage caused by administration of a non-steroidal anti-inflammatory agent, and symptoms associated with lumbar spinal canal stenosis, comprising the crystal of any one of claims 1 to 3 as an active ingredient.
An accelerating agent for angiogenic therapy in gene therapy or autologous bone marrow transplantation, comprising the crystal of any one of claims 1 to 3 as an active ingredient.
An accelerating agent for angiogenesis in restoration of peripheral artery or angiogenic therapy, comprising the crystal of any one of claims 1 to 3 as an active ingredient.
A method for producing a Form-I crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl) acetamide, characterized in that 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide is dissolved in an alcoholic solvent or a mixed solvent of an alcoholic solvent and a ketone solvent while heating, and subsequently is crystallized by cooling the solution gradually.
A method for producing a Form-II crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl) acetamide, characterized in that 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide is crystallized from an alcoholic solvent, a ketone solvent, a saturated hydrocarbon solvent, an ether solvent, and water or a mixed solvent thereof.
A method for producing a Form-III crystal of 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl) acetamide characterized in that 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butyloxy}-N-(methylsulfonyl)acetamide is crystallized from an ester solvent or an aromatic hydrocarbon solvent.